Matias Zeledon of Down to Earth Coffee in Costa Rica posted an interesting picture of coffee beans with different sizes on the branch. This is an example of why you have to hand pick coffee to only get the ripe cherries. Here is Matias’ description:

Happy to see the coffee healthy and developing well in the Providencia highlands farm. The different sizes of the green beans are produced by the different waves of blooming, which generate the different stages in the harvest. The big differences in size comes from the fact that this year we had rain on Feb 9th so the first blooming came early and that is why the beans look so well developed compared to the others. This also means that we are going to be harvesting coffee in early November, a sizable bunch and not just a few.

In Coffee Smoothie ONE I showed how to make a coffee smoothie with freshly ground coffee. Since writing that post I have probably made a hundred of them and have perfected the recipe.

First I purchased a few bottles of Lorina Lemonade at the grocery store. The drink is amazing but what I really wanted was the resealable bottles.

Lorina Lemonade bottles

The bottles are strong and the seal is both interesting and functional.

Cold Brewed Coffee Syrup
Next rather than making small batches of coffee syrup I moved to a 12 cup French Press. I put in 150 grams of coffee and fill with water. After sitting 24 hours in the fridge I get a full bottle of syrup. This is basically triple strength.

The other bottle is sugar syrup. I tried cocoa rather than Quik and really liked the result. You have to change the amount of sugar syrup as cocoa has no sugar or sweetener in it.

The last change was adding a banana. One issue with the original recipe is the drink tends to separate into the ice on top and the fluid below. The banana adds a pulp that keeps the drink from separating. It also is more creamy.

Caffeine is released during roasting. Some of this caffeine crystalizes on the outside as the smoke escapes.

Temperature Probe Setup on HotTop Roaster

This is a HotTop roaster. The yellow devices on top are temperature probes. As the roast progresses, smoke escapes from the probe holder. Over time, amazingly intricate white crystal structures appear. These caffeine crystals are know as angel hair in coffee jargon.

Caffeine Angel Hair formed on the bean temperature probe handle

These are microscope shots of the crystals after removed from the probe.

The degassing experiment three was drawing to a close. To recap 100 grams of dark roasted beans were put in one flask, 100 grams of the same beans but ground were put in the other flask. After 24 hours 294 mls of CO2 were released from the ground coffee. Even after 3 days the ground coffee maxed out at 300 mls supporting the literature (1) that ground coffee degasses in 12-24 hours depending on grind.

The whole beans were a different story. The 130 ml of day one grew to 290 mls in nine days. The literature said about 7 days for most degassing. I was getting ready to clean up the experiment when I had an idea. Just for “shits and giggles” why not grind the nine day old beans. They had stopped releasing CO2 but was there any inside that grinding would release? Using the same grinder settings as previous experiments I ground the 100 grams and quickly returned to the flask and stoppered. I was surprised to see gas released with a similar curve to freshly roasted coffee.

In one day 112 mls of CO2 were released. Like fresh roast beans almost all of the release was in the first 24 hours. While only 38% of what a fresh roast grind release, the total release was 406 mls versus 296 for fresh ground.

Grind Nine Day Old Beans

I have not found any literature on CO2 degassing in older coffee. I am going to continue other degassing experiments to open up the parameters of cause/effect.

Experiment three was a chance to apply all of the lessons learned in measuring CO2 degassing of roasted coffee.

Degas 3 Setup

Lesson 1: A photo copy stand was used to support the graduated cylinders. Fill the cylinders with water and place upside down in the tank. Lower the photo rack then support the cylinders with square wooden rods, hold with several rubber bands then raise the attached cylinders with the camera holder adjuster.

Eye Droppers on TubingLesson 2: Using eyedroppers is very effective but you have to slightly point them downhill or the air will escape, just slower. The most effective dropper has a turn on the end pointing down. This made it easier to prevent gas escaping and water filling the line. The eye droppers were purchased at Walmart for $2 a pair. Keep the eyedroppers as close to the cylinder bottom without touching. Water pressure becomes a factor if you put them deep in the water.

Flask with Funnel on ScaleLesson 3: The critical timing is from grinding the coffee, place in the flask, weigh and stopper. By putting a funnel in the flask on the scale ground coffee could be scooped quickly and accurately.

Lesson 4: I wrote a trivial program to log the time vs the readings. This meant recording readings was just typing in the levels. The program tracked the time. For the time value I used a Unix Timestamp, the number of seconds since January 1 1970 00:00:00 GMT. So to calculate offset is simple subtraction from the first reading. The data was then copy/pasted into a spreadsheet for calculations and graphing.

Costa Rica Degas Exp 3 w Degas 2 in BackgroundLesson 5: Track as many variables as possible. By using Artisan I could compare degas roast 2 to degas 3 roast.

Hours

Ground ml CO2

Whole ml CO2

–

30

0

0.05

45

0

0.10

58

0

0.12

62

0

0.13

66

0

0.18

75

0

0.20

80

0

0.27

90

0

0.34

100

0

0.44

110

0

0.51

118

0

0.53

120

0

0.65

130

0

0.75

136

0

1.04

154

0

1.17

160

0

1.28

165

0

1.76

183

15

1.94

190

18

3.79

226

37

11.69

270

89

12.12

280

94

22.12

290

124

23.36

290

126

24.04

290

128

24.58

294

130

25.61

296

132

27.25

296

135

35.65

296

145

36.87

296

154

46.35

300

170

47.62

178

48.65

182

50.75

182

59.44

188

60.89

194

72.75

198

85.32

210

91.38

220

100.10

227

108.91

236

111.60

240

114.28

243

117.01

246

120.31

248

155.70

264

157.01

267

166.09

270

Hours vs ml CO2 Ground (Blue) vs Bean (Red)

Conclusion 1: Ground degassing is pretty well complete in this experiment at 12 hours. 280 ml of CO2 released at 12 hours while 300 by 48 hours. After day 3 the whole beans are still degassing but slowing down.

Next experiment is to repeat this setup but with a medium roast (430o drop.) I also ordered a school grade color spectrometer and am investigating roast colour analysis.

Most Important Conclusion: Crawling into the raw science basics of roasting is really fun.

In this experiment, I roasted Costa Rica coffee to Full city. I dropped the roast at 450oF. While I normally do not roast so dark, I knew from documentation this would result in more CO2 to be released.

Ground on left vs Whole Bean on Right

I placed 100 grams of ground coffee in the the left flask, while 100 grams of whole beans were placed in the right flask. I loaded the ground coffee into the flask as quickly as possible, but the degassing speed surprised me. In one hour of capping the flask, 120 ml of CO2 was already released. This is much faster than whole bean degassing. In the previous whole bean experiment with a medium roast and twice the coffee it took 24 hours to release 120 ml.

Another change from the previous setup was to add eye droppers to the end of the tubes. This made it easier to see the bubbles form. Play the video to see how fast the ground coffee released CO2.

Eye Droppers on Tubing

Hours

ml CO2

0

0

0.08

28

0.13

40

0.23

58

0.27

62

0.28

65

0.35

72

0.38

78

0.45

84

0.52

90

0.60

96

0.67

102

0.80

110

0.90

116

0.95

118

1.00

120

1.07

126

1.15

130

1.37

138

1.48

144

1.88

158

2.00

160

2.30

166

3.13

186

3.53

194

5.00

212

6.83

228

8.78

238

19.00

256

31.00

268

ml CO2 Released vs Hours

Roast profile from the Artisan tracking screen.

Costa Rica Roast Profile for Degas 2 Experiment

Degassing Grind w 1/16" Scale
This shot image was captured with a Celestron digital microscope. The scale on the right is 1/16″. The beans were ground with a Macap MC4.

As I read more and more on how CO2 is released from freshly roasted coffee I decided to try my own experiment. Basically the experiment is to measure the captured CO2 as it is released. A basic experimental approach is to use an eudiometer.

Eudiometer as shown in Wikipedia

My setup is not quite as elegant.

First Degas Measurement Experiment Setup

The purpose of this test is to try the setup. The flask is 500 ml with 211 grams (~7.4 oz.) of medium roast Costa Rica coffee. The beans were loaded 5 minutes after dump with a temperature of 94oF. The graduated cylinder is 250ml and the tubing 1/4″ OD flexible copper. I am concerned that the inside diameter is large enough that air will escape up and water flow down. I will add a water dropper on the next version to keep water from going in and the air bubbling out. Also the tube should be shorter so that it is easier to get into the graduated cylinder.

12 hours into degassing

Hours

ml CO2

1.4

20

3.7

29

11.7

76

13.0

80

19.0

100

22.0

112

24.0

122

24.6

124

26.0

129

36.0

152

37.0

154

46.5

172

48.0

176

49.5

180

59.5

194

61.0

200

71.0

214

84.0

224

94.5

236

104.3

246

108.0

250

ml CO2 Released vs Hours

The papers I found said the degassing would continue on whole beans for 7 days. Now that the output reached 250 ml, the capacity of the graduated cylinder, I am going to end this experiment and set up one comparing whole bean and ground coffee. To avoid the 250ml capacity I will put in 100 grams of coffee.